John davis, a manager of a supermarket, wants to estimate the proportion of customers that will be using food stamps at his store. how large a sample is required to estimate the true proportion to within 3% with 98% confidence?

Usually when encountered with questions that relate with how large a sample should be to yield a significant result is answered by determining the sample size. The sample size is the determination of how much sample is needed for the study to reveal confidence levels of 98% or higher.

Because the population is not given in this proportion, an exact number cannot be revealed. However it might be that the sample is dependent on the nature of the study where Davis plans to exhibit. 

if the eqn of the parabola is f(x) = (x-4)(x+2), we need to mult. this out to find the coordinates of the vertex.

then f(x) = x^2 + 2x - 4x - 8, and f(x) = x^2 - 2x - 8.

one way in which you can find the vertex is to calculate x = -b / (2a).   here, that comes to

        )

x = = 1.   f(1) = 1^2 - 2(1) - 8 = - 9.   vertex is at (1, -9).

        2(1) 

find another point on the curve:   let x=0, for which y=-8.   then (0, -8) is on the curve.   plot the vertex and this point and draw a smooth parabola thru both.

hope this